Improvement in adjustable guards for screw-propellers



' A. MARSCHALL.

ADJUSTABLE GUARDS FOR SCREW-PROPELLERS.

No. 191,007- Patented May 22,1877.

ml'nesses Inventor:

222 M y 'z Z M.

N. PETERS, FHOTO-LITHOGRAPHER. WASHINGTON. ,D C.

UNITED STATES PATENT OFFICE.

AUGUST MARSGHALL, OF NEW YORK, N. Y.

IMPROVEMENT IN ADJUSTABLE GUARDS FOR SCREW-PROPELLERS Z Specificationforming part of Letters Patent No. 191,007, dated May 22, 1877application filed March 10, 1877.

To all whom it may concern:

Be it known that I, AUGUST MARSCHALL, of the city of New York, countyand State of New York, have invented an Improvement in Screw-Propellers,of which the following is a specification This invention relates to animprovement on boats which are driven by means of screwpropellers andtravel through narrow or shallow water-courses, such as canals or thelike.

The invention has for its object to prevent the swell of the watercreated by the revolution of the propeller from washing and injuring thebanks of the canal or stream and consists in placing at each side of thepropeller a shield, which is attached to the hull of the Vessel, andwhich, while allowing free access of the water to the propeller, Willpractically prevent the formation of any lateral swell or wave.

The invention also consists in the details of construction hereinafter.more fully pointed out. I

In the accompanying drawing, Figure 1 is a side view of the stern partof a boat provided with my improvement. Fig.2 is a stern view of thesame.

Similar letters of reference indicate corresponding parts in bothfigures. V

The letter A represents the hull of a canal or other boat, of suitableconstruction. B is the screw-propeller thereof. 0 is a shield, oftubular or other form, and provided with a large number of smallperforations, and made of metal orother proper material. This shield G,if made tubular, as in Fig. 2, encircles the propeller B, and isfastened to the stern of the boat A in suitable manner. I prefer tofasten it, however, in the manner indicated in the drawing-that is tosay, by rods ac, attached to, and projecting forward from, the shield,and passing through corresponding eyes b b, that are applied to the hullof the boat near the stern thereof. By using this mode of attachment theshield O can be adjusted lengthwise on the boat to regulate its effect;but other suitable fastenings may be employed.

The shield 0 should be of such interior diameter that it allows freerevolution of the screw-propeller, and is open at both ends, so that thewater may freely reach the propeller through the front and be dischargedat the rear of the shield. In this way the efficiency of the propellingmechanism is in no wise diminished; but the shield, though allowing thewater to pass through its perforations, will break up and destroy anylateral swell created by the propeller, and prevent, in consequence, allinjury to the banks of the canal or other water-passages through whichthe boat passes. If the shield is not perforated, it will also destroythe lateral swell but it is then not as efficient as a perforatedshield.

Instead of making the shield tubular, it may be made of other suitableform, as the essential feature of this invention consists in theapplication of a shield to each side of the screw-propeller of a vessel.

I am aware that previous to my invention cylindrical shields havinginner projections or blades have already been placed around propellersbut the vanes served, by dammin g the water, to retard the action of thepropeller, and to render, therefore, the entire attachment useless.

I claim as my invention- 1. The combination of a propeller, B, with theperforated encircling shield G, which is entirely smooth on its innerside, substantially as and for the purpose herein shown and described.

2. The adjustable shield O, herein described, fastened to the body of avessel, A, by means of rods a and eyes b, substantially as specified.

AUGUST MARSOHALL.

Witnesses:

ERNEST O. WEBB, F. V. BBIESEN.

